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O. H. W. Siegmund (Space Sciences Lab, UCB)
Many advances in photocathodes (GaN, Diamond, etc), microchannel plates (Si MCPs), cryogenic detectors (superconducting tunnel junctions, STJs), intensified active pixel sensors, and readouts (cross strip) are poised to make a significant impact on the capabilities of future instruments.
GaN photocathodes have been produced with > 30 percent DQE in the UV, with cutoffs around 400nm, and diamond photocathodes have been made with 40 percent DQE and cutoff > 200nm.
Si MCP samples of 25mm format with ~ 7 micron pores, have been evaluated. Gain of nearly 10,000 for a single Si MCP has been achieved. The quantum detection efficiency for Si MCPs is the same as glass MCPs. The background is as low as ~ 0.02 events sec/cm2, the best for any MCP. Flat fields are free of any modulation, and the gain uniformity is relatively good. Along with low stopping power for x, gamma and cosmic rays, and stability to high temperatures (> 800 C), Si MCPs are chemically compatible with many photocathodes.
The cross strip anode is a multi-layer metal and ceramic cross strip pattern. Event positions are encoded by direct sensing of the charge on each strip and determination of the charge cloud centroid for each event. The spatial resolution (5 microns) achieved is sufficient to resolve 7 micron microchannel plate pores while using low MCP gain. Image linearity is good enough to see distortions in the microchannel plate pore alignment, and the low MCP gain will enhance the overall lifetime of MCP detector systems.
STJs show very high detection efficiencies and can detect radiation from the X ray through to the infrared. Their low effective band gap allows reasonable non-dispersive energy resolution at the higher photon energies. In addition small arrays of STJs have been successfully made.
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Bulletin of the American Astronomical Society, 34
© 2002. The American Astronomical Soceity.